Landscapes with wild bee habitats enhance pollination, fruit set and yield of sweet cherry

Abstract

More than 70% of the leading global food crops, accounting for 35% of the global food production, are affected by pollination of flower-visiting animals, but the main pollinators – managed honey bees and wild bees – are currently declining in many regions worldwide. For the vast majority of crops it is unknown whether managed honey bees or wild bees are the most efficient pollinators, and how the pollination service provided by wild bees can be ensured.We assessed in a landscape-scale study how sweet cherry production is influenced (1) by high-diversity bee habitats, and (2) by flowering ground vegetation which might compete with cherry for pollinators or might facilitate cherry pollination.Cherry was highly dependent on insect pollination with bagged flowers producing only 3% of the fruits produced by open-pollinated flowers. Although two thirds of all flower visitors were honey bees, fruit set was related to wild bee visitation only, presumably due to their higher pollination efficiency. Initial fruit set and final cherry yield were closely correlated. Wild bee visitation increased with the proportion of high-diversity bee habitats in the surrounding landscape (1km radius). An increase of high-diversity bee habitats in the landscape from 20% to 50% enhanced fruit set by 150%, which was experimentally shown to be due to pollen limitation. Neither flower cover of ground vegetation nor bee densities on ground transects were related to flower visitation in trees or fruit set.Our results show that pollination services by wild bees in cherry surpassed pollination by honey bees. Hence, farmers need to protect semi-natural habitats in their landscapes to guarantee pollination and high yields. The conservation of semi-natural habitats, which provide nesting sites and additional food resources before and after cherry flowering enhances gratis ecosystem services, and thereby, the farmer’s yield.